Response: Zika virus is recognized as a cause of microcephaly and other severe birth defects when a woman is infected during pregnancy. Additionally, it has been associated with potentially fatal complications, such as Guillain-Barré syndrome. It is not well understood how often Zika virus particles can be detected in semen and other body fluids and for how long they remain detectable. Existing evidence is based on case reports and cross-sectional observations, primarily from returning travelers. A more comprehensive description of the dynamics of the early stages of Zika virus infection, observed within infected people over time, is needed to inform diagnostic testing as well as prevention recommendations and interventions.MedicalResearch.com: What are the main findings?

Response: CDC and partners conducted a study beginning in May 2016 in Puerto Rico to investigate how frequently and for how long Zika virus could be found in different human body fluids.

Our paper and presentation represent an interim analysis providing early results based on the first 150 of the more than 300 people expected to be enrolled. Participants diagnosed with Zika provided samples of blood serum, saliva, urine, and semen or vaginal secretions for regular testing over a 6-month period. This study is unique in that 92% of participants were enrolled within 1 week after symptoms of Zika began, providing a clearer understanding of virus detection early in the course of infection. It is also the first study to examine multiple body fluids for the presence of Zika virus in an ongoing fashion. The study found that Zika virus particles (RNA) were more likely to be found in serum than in urine. In serum, half of participants had detectable RNA at 14 days after the start of symptoms, with 5% still having detectable RNA at 54 days. In urine specimens, half of the participants had Zika RNA at 8 days, with 5% still having detectable RNA at 39 days. In this study, Zika virus remained the longest in semen; half of participants had RNA in their semen 1 month after the start of symptoms, and about 5% still had detectable RNA after 3 months. Outside this study there have been only two case reports of men whose semen still had detectable Zika for more than 6 months after symptoms began. Based on our findings, such late detection seems unusual. It remains unclear whether those with detectable RNA pose an infection risk to partners at these time points. Zika virus particles were largely not detectable in saliva and vaginal fluids among participants in this study after 1 week.

MedicalResearch.com: What should readers take away from your report?

Response: For pregnant women who have recently traveled to an area with Zika, their healthcare provider can order a blood test to evaluate if they currently are or were recently infected with Zika. For all other people who recently traveled to an area with Zika and had symptoms of an illness similar to Zika (fever, rash, joint pain, or red eyes), diagnostic testing can be ordered by a medical provider. Zika virus diagnostic testing is not currently recommended for non-pregnant people who have not had signs or symptoms consistent with Zika.

Understanding how often and for how long evidence of Zika virus can be found in different body fluids can improve testing methods and could have implications for prevention and education efforts. Our findings support current sexual transmission recommendations. CDC recommends that men with possible Zika virus exposure use condoms or not have sex for at least 6 months from the beginning of symptoms or from last exposure; women with possible Zika virus exposure should wait at least 8 weeks from beginning of symptoms or most recent exposure before trying to become pregnant. CDC recommends that people with potential exposure to Zika virus avoid donating blood for at least 120 days, or 4 months.

MedicalResearch.com: What recommendations do you have for future research as a result of this study?

Response: The data presented in this study suggest that blood serum was more reliable than urine for detecting Zika virus genetic material. However, about 10% of participants only tested positive in urine and not in serum. Therefore, there is some modest benefit in testing both urine and serum in patients with suspected Zika virus infection; our findings support current diagnostic recommendations to test paired blood and urine specimens. It would be useful for future studies to confirm this findings. Furthermore, our study did not address the risk of sexual transmission of the Zika virus. This is an important question that remains to be answered.

MedicalResearch.com: Is there anything else you would like to add?

Response: Published information on the duration of Zika virus in semen has been limited to individual case reports or small case series, and mostly on returning travelers. Among the multiple published studies, only two case reports have found Zika virus particles in semen beyond 6 months. Our study was designed to answer questions around how long the virus can be detected and has several strengths, including enrolling people early after symptoms began, following up with people over time at established visits, and collecting different body fluids among participants. The results of this study demonstrated that in most cases, Zika is no longer detected in semen after 3 months from when symptoms began and it is likely that the risk of spreading it to others is minimal at 6 months. Therefore, CDC will continue to recommend that men who have been exposed to Zika should use condoms or not have sex for at least 6 months from the start of symptoms or from their last exposure. CDC still recommends that women who have been infected with or exposed to Zika virus wait at least 8 weeks from the beginning of symptoms or last exposure before attempting to become pregnant. These results were part of an interim analysis and several participants still had detectable Zika virus particles at their most recent visit. We will continue to follow up with participants, and estimates on how long evidence of Zika stays detectable in the body will be updated once complete information is available.

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